There is a market for it. Not every human sits everyday watching interest rates, stock prices or other financial signals. I, for one, am glad that banks are competing for money with any interest rate.
Definitely. For so long, $100K or whatever sitting as a cash or near-cash reserve, it really didn't matter much whether that was in a checking account, a savings account, or a brokerage sweep account. But getting 4-5% on that kind of money at very low risk is getting to be real money at current interest rates and it's worth actively managing how much you have in a checking account.